Here are some random tips based on my own Spore experience.
Save the game! It doesn't automatically save, not even between stages (which seems strange to me), so be sure to save often.
Any cinematic you don't want to watch can be skipped by hitting the Esc key. This includes growing up from a baby to an adult after death.
I'm not sure exactly how Spore populates each play-session, but it obviously gives preference to whatever is in your personal Sporepedia. So if you want a lot of variety between playthroughs, be sure to hop online with your Sporepedia and download lots of stuff.
Find buddies. The other day, I told a friend that one of her creatures kept stealing my tribe's food. Being able to share funny stories like that with friends makes the game much more enjoyable. If you add me (hallower), I'd certainly love to hear what mischief my creations are up to in your game.
Object orientation is often about finding the right camera angle from which to adjust.
If you make only a few changes to your creature at each evolution, then your creature's History timeline will be more meaningful.
Stay far away from Epic creatures! There can be more than one per planet, they like to wander, and they can even attack spaceships if they have a ranged attack! I lost a ship that way.
Numbers matter! Always keep your pack full. This will often be the difference between success and failure, life and death. Even if you're completely outmatched by an attacker, you can always leave your mate as a convenient decoy as you run!
If you're going to form a pack, choose an Alpha as your mate. Your nest won't always have an Alpha (leader), but look for one. Alphas are tougher than the rest of your species.
To socialize with other species, try to isolate members or find loners. If you start to socialize near a group, then you'll have to compete with that whole group's combined social power. The socializing bar will move faster for whoever has mates helping.
If your creature is social, be sure to create alliances with other species. I once had three of my species in my pack, plus four of another species, plus two of yet another species all travelling together. This small army made converting other creatures to my side a breeze.
Keep in mind when you're finalizing your creature before Tribal that you'll want free space to fit clothes on.
Killing an epic creature will keep your tribe well fed for a good while. My tribe of 12 returned to carve out more meat over and over.
In Tribal, you can domesticate animals even as a warrior tribe, but you must have extra food to offer them initially.
In a typical RTS game, you can choose to build your empire slowly and finally make your move after you've built up. That's not an option in Spore. You get upgrades by conquering or forming alliances with other tribes, so try to hop on this quickly. I only take my guys out to harvest food once and fill my tribal population before making my first move against/for another tribe.
To enter Civilization and save your game once you choose to progress from Tribal, you must design a city hall and vehicle. If you need to take a break from the game, remember that you can go back and edit your building and vehicle, or create new ones, later.
Turrets are cheap. Build up your cities' defenses and you won't have to worry as much about invasion while you're off doing other things.
As I said yesterday, don't spread yourself too thin. Space stage offers a lot of room for personal strategy, but it's easy to become overwhelmed by trying to do too many things at once or exploring too quickly (assuming you care what happens to your former colonies). The money you spend money on ship upgrades can also go to colony development or defenses (turrets). If you explore many planets quickly, like I did, then you might have to deal with more civilizations and planets than you have the resources and time to handle easily.
I'll add more tips if I think of some.